Inlet box for centrifugal fans



March 14, 1944. J, cAs slE INLET- BOX FOR CENTRIFUGAL mus Filed July.10, 1942 Imam/ 202 flamiiea %JCP via neg Patented Mar. 14, 1944 mLETBOX FOR CENTRIFUGAL FANS John Cassie, Dedham, Mass, assignor to B. F.

Stur'tevant Company, Boston, Mass.

Application July 10, 1942, Serial No. 450,369

Claims.

This invention relates to inlet boxes for centrifugal fans. Rectangularinlet boxes are usually provided at the axial inlets of centrifugal fansfor connection to the inlets and to ducts which convey air to be actedupon by the fans. Losses occur in such inlet boxes which result inreductions in the expected performances of the fans with which they areused.

This invention reduces the losses in a rectangular inlet box byproviding in the inlet box, air guide vanes which prevent the air fromspinning in the box and which prevent the air entering the box fromcrowding directly toward the axial inlet of the fan.

In one embodiment of the invention applied to a centrifugal fan having ahorizontal shaft on which a fan wheel is mounted, a rectangular inletbox has a vane which extends from its air inlet in a plane parallel tothe plane of the axial inlet of the fan, to a point adjacent the axialinlet and which divides the inlet passage in the box into twosubstantially equal portions. This vane acts to prevent the air enteringthe inlet box from being drawn by the suction of the fan directlytowards the axial inlet without filling the inlet boxas it should.Another vane extends perpendicular to the other vane, the length of theinlet box except for a gap for clearing the fan shaft. This vane dividesthe inlet box into two substantially equal passages, one below and theother above the fan shaft, and its function is to prevent the air in theinlet box from spinning as it enters the axial inlet to the fan wheel.The two vanes provide cellular construction for bracing the inlet anddispense with the need for external bracing.

Use of the two vanes of this invention results not only in improved fanperformance but in the reduction in size of the inlet boxes and as aresult of the latter, in reducing the distance between the pedestals forsupporting the fan shaft, and the overall width of the fans.

Objects of the invention are to improve the efiiciency of air flow inrectangular inlet boxes; to reduce the sizes of rectangular inlet boxes,and to reduce the sizes of fans with which rectangular inlet boxes areused.

The invention will now be described with reference to the drawing, ofwhich:

Fig. 1 is an elevation view of a centrifugal fan equipped with an inletbox of this invention, the inlet box being shown in section, the sectionbeing taken along the lines I-l of Fig. 2, and

gal fan equipped with inlet boxes embodying this invention.

The fan 5 has the wheel 6 mounted on the shaft 1. The axial inlets 8conduct air into the wheel. The air from the wheel is delivered throughthe outlet 9.

The inlet boxes ID are attached in the conventional manner to theopposite sides of the fan and have the rectangular air discharge outletsH adjacent and in substantial alignment with the axial inlets 8. a

The inlets I2 ofthe inlet boxes are connected in the conventional mannerto the ducts l3 which conduct air to the fan.

The vertical vanes l4 extend between the upper and lower walls of theboxes 18, from the inlets l2 thereof to points substantially midwaybetween the inlets I2 and the shaft 1. The purpose of these vanes is toprevent the air entering the inlets l2 of the boxes ID at the pointsmost distant from the axial inlets 8 from flowing directly towards andinto the inlets 8. The vanes i4 force the air entering the inlets [2 atthe points most distant from the inlets 8 to travel a con.-

siderable distance into the boxes before it can be drawn by the suctionof the fan into the inlets 8. Thus the inlet boxes are fully loaded bybeing filled with air and there is no short circuit flow.

The vanes l5 bisect the inlet boxes along a horizontal plane extendingthrough the shaft 1 and are provided with openings as illustrated byFig. 1 for permitting the shaft to extend therethrough. The air in itsmovement through the inlet boxes towards the axial inlets 8 to the fanwheel 6, may tend to spin because of some condition upstream of theinlet boxes. The vanes i5 stop the spin and guide the air on oppositesides thereof without spin into the axial inlets 8.

The vanes l4 and I5 are attached to each other and to sides of the inletboxes ill by the structural angles l6 and form cellular supportingstructures which enable the boxes to be constructed with thinner wallsand which eliminate the need for external bracing.

The inlet boxes provided with the vanes as described are so efficient inhandling the air without turbulence and without spin that they increasethe performance of the fan with which they are used substantially tothat which would be attained by the same fans without inlet boxes. Theyalso are greatly reduced in width (measured along the shaft of the fans)enabling the pedestals of the fans to be moved closer together, thusreducing the size of the fans and Fig. 2 is an end view of a doubleinlet centrifuproviding saving in material.

For example, on a given system of duct work, 35,000 cubic feet perminute of air at a static pressure of 3.96 inches of water, at a motorspeed of 900 R. P. M. is desired. A given fan will give this performancewith free inlets. Adding the usual inlet boxes results in a reduction involume to 31,200 C. F. M. and a reduction in pressure to 3.14".Substituting the inlet boxes of this invention results in bringing backthe performance substantially to that of the free inlet condition.

The inlet boxes embodying this invention may be reduced in width(measured along the axis of the shaft) about 20%. Otherwise the outsidedimensions of the inlet boxes are conventional.

While the vanes I4 have been referred to as vertical and the vanes l5 ashorizontal, the fan housings may, of course, be rotated for convenientplacement and connection to duct work so that the vanes may be placed atangles to their described positions.

While one embodiment of this invention has been described for thepurpose of illustration, it should be understood that the invention isnot limited to the exact apparatus and arrangement of apparatusillustrated as modification thereof may be suggested by those skilled inthe art Without departure from the essence of the invention.

What is claimed is:

1. A rectangular inlet box for a centrifugal fan having a shaft, saidinlet box having an outlet arranged centrally around said shaft andhaving an inlet extending in a plane substantially parallel to saidshaft, a vane in said box extending from said inlet, substantiallyperpendicular to said plane and said shaft and terminating short of saidshaft, anda second vane in said box extending substantiallyperpendicular to said first mentioned vane, said second vane extendingin a plane intersecting said shaft from said inlet to the opposit sideof said box and having an opening therein for the passage of said shafttherethrough.

2. A rectangular inlet box for a centrifugal fan having a shaft, saidinlet box having an outlet arranged centrally around said shaft andhaving an inlet extending in a plane substantially parallel to saidshaft, a vane in said box extending from said inlet, substantiallyperpendicular to said plane and said shaft and terminating short of saidshaft, and a second vane in said box extending substantiallyperpendicular to said first mentioned vane, said vanes extendingsubstantially along the center lines of said box.

3. A rectangular inlet box for a centrifugal fan having a shaft, saidinlet box having an outlet arranged centrally around said shaft andhaving an inlet extending in a plane substantially parallel to saidshaft, a vane in said box extend ingsubstantially perpendicular to saidplane and said shaft and terminating short of said shaft, and a secondvane in said box extending substantially perpendicular to said firstmentioned vane, said second vane extending in a plane intersecting saidshaft, from said inlet to the opposite side of said box, and having anopening therein for the passage of said shaft therethrough, said firstmentioned vane being located substantially half Way between said outletand the side of said box opposite thereto.

4. A rectangular inlet box for a centrifugal fan having a shaft, saidinlet box having an outlet arranged centrally around said shaft andhaving an inlet extending inav plane substantially parallel to saidshaft, a .vane in said box extending from said inlet, substantiallperpendicular to said plane and said shaft and terminating short of saidshaft, said vane being located substantially half way between saidoutlet and the side of said box opposite thereto.

5. A rectangular inlet boxfor a centrifugal, fan having a shaft, saidinlet box having an outlet. arranged centrally around said, shaftand'having an inlet extending in a planesubstantially parallel to saidshaft, and a vane in said box extending in aplane intersectingsaidshaft, from said inlet to the side of said box opposite thereto, andhaving an opening therein for the passage of said shaft therethrough,said vane dividing said box into two substantially equal air passagesfor supplying air from said inlet into said outlet.

JOHN CASSIE.

